The invention relates to a method for operating a radio communication system in which a frequency band split into a plurality of sub-bands is used for communication between network radio stations and subscriber stations.
In radio communication systems, messages, for example with voice information, image information, video information, SMS (Short Message Service), MMS (Multimedia Messaging Service) or other data are transmitted with the aid of electromagnetic waves via a radio interface between transmitting and receiving station. In this context, the stations can be various types of subscriber stations or network radio stations such as repeaters, radio access points or base stations depending on the actual design of the radio communication system. In a mobile radio communication system, at least some of the subscriber stations are mobile radio stations. The electromagnetic waves are radiated with carrier frequencies which are in the frequency band provided for the respective system.
Current mobile radio communication systems are often constructed as cellular systems, e.g. according to the GSM (Global System for Mobile Communication) or UMTS (Universal Mobile Telecommunications System) standard with a network infrastructure including e.g. of base stations, facilities for monitoring and controlling the base stations and other network facilities. Apart from these cellular, hierarchic radio networks organized over a wide space (supralocal), there are wireless local area networks (WLANs) with a radio coverage area which, as a rule, is much more limited in space. Examples of various standards for WLANs are HiperLAN, DECT, IEEE 802.11, Bluetooth and WATM.
The access of subscriber stations to the common transmission medium is regulated by multiple access methods/multiplex methods (MA) in radio communication systems. In these multiple accesses, the transmission medium can be split between the subscriber stations in the time domain (Time Division Multiple Access, TDMA, in the frequency domain (Frequency Division Multiple Access, FDMA), in the code domain (Code Division Multiple Access, CDMA) or in the space domain (Space Division Multiple Access, SDMA). Combinations of multiple access methods are also possible such as e.g. the combination of a frequency division multiple access method with a code division multiple access method.
To achieve the most efficient transmission of data possible, the entire available frequency band can be split into several sub-bands (multicarrier method). The concept forming the basis of the multicarrier systems is to transfer the initial problem of transmitting a wide-band signal into the transmission of several narrow-band signals. Among other things, this has the advantage that the complexity required at the receiver can be reduced. Furthermore, dividing the available bandwidth into several narrow-band sub-bands provides for distinctly greater granularity of the data transmission with regard to the distribution of the data to be transmitted between the different sub-bands, i.e. the radio resources can be distributed to the data to be transmitted or to the subscriber stations, respectively, with great fineness. An example of a multicarrier transmission method is OFDM (Orthogonal Frequency Division Multiplexing), in which pulse shapes which are approximately rectangular in time are used for the sub-bands. The frequency spacing of the sub-bands is selected in such a manner that in the frequency space for the frequency at which the signal of a sub-band is evaluated, the signals of the other sub-bands have a zero transition. The sub-bands are thus orthogonal to one another.